This document discusses sterilization and disinfection. It begins by explaining how sterilization grew from efforts to prevent bacterial infection and notes key historical figures like Nicolas Appert, Louis Pasteur, and Joseph Lister who advanced methods of preservation and sterilization. It then defines terms like sterilization, disinfection, and antisepsis. The document outlines various physical and chemical methods for killing microorganisms, including heat, filtration, radiation, and chemical disinfectants. It emphasizes that sterilization is important in healthcare settings to prevent the spread of disease.

2. ⦁ Sterilization grew partly out of preservation
and also by trying to prevent infection caused
by bacteria
⦁ Nicolas Appert-1809 heat as a preservative
method
⦁ Louis Pasteur -1865 invented pasteurization.
⦁ Charles Chamberland –1879 invented
pressure steam sterilizer (autoclave)
⦁ Joseph lister-1880 invented carbolic acid
spray.

4. WHY NEEDED?
⚫Microorganisms are ubiquitous.
⚫Since they cause
contamination, infection and
decay, it becomes necessary to
removeordestroy them from
materialsor from areas.
⚫This is theobject of sterilization.

5. DEFINITIONS
⚫Sterilization – process by which an article, surface or
medium is freed of all living microorganisms either in the
vegetativeorspore state.
⚫Disinfection – destruction or removal of all pathogenic
organisms. (sanitization w.r.t. Food processing and
catering)

6. ⚫Antisepsis – prevention of infection, usually by inhibiting
thegrowth of bacteria in wounds or tissues.
⚫Antiseptics – chemical disinfectantswhich can be safely
applied to skin or mucous membrane and are used to
prevent infection by inhibiting growth of bacteria.
⚫Bactericidal – agentwhich can kill bacteria.
⚫Bacteriostatic – agentwhich only prevents multiplication
of bacteria.

7. HOW CAN MICROORGANISMS BE KILLED
• Denaturation of proteins
• Oxidation
• Filtration
• Interruption of DNA synthesis/repair
• Interference with protein synthesis
• Disruption of cell membranes

8. Most Resistant
Endospores
Mycobacteria
Fungal spores
Small non-enveloped viruses (polio, rota virus, rabies)
Vegetative fungal cells
Enveloped viruses (Herpes, Hepatitis B and C, HIV)
Vegetative bacteria
Least Resistant

9. PRINCIPLES OF STERILISATION
1. Thorough cleaning of instruments before
sterilisation.
2. Contact of sterilizing agent with all surfaces of
each item for specified period of time at
specified temperature.
3. Regular service and maintenance of sterilizing
equipment.

10. ⦁ Proposed by Earl H. Spaulding
⦁ Categorized into 3 categories
Critical devices
Semi critical devices
Non critical devices

11. PHYSICAL METHODS CHEMICAL METHODS
S
T
E
R
I
L
I
S
A
T
I
O
N
Sunlight
Drying
Heat •Dry heat
•Moist heat
Filtration
Radiation
Alcohols
Aldehydes
Dyes
Halogens
Phenols
Surface-active agents
Metallic salts
Gases

12. PHYSICAL METHODS OF
STERILISATION

13. SUNLIGHT
❖ Possesses bactericidal activity.

14. HEAT
❖ Most reliable method.
❖ Can be used either in dry form or moist form.

15. DRY HEAT STERILISATION
❖ Principle - Killing effect is due to
protein denaturation
•
• oxidative damage
.
.

17. FLAMING
❖ Bunsen flame is used.
❖ Uses – Scalpel blades, inoculation wires and
loops, glass slides, cover slips.

18. INCINERATION
❖ Excellent method.
❖ Materials are reduced to ashes by burning.
❖ For contaminated and pathological materials
at a high temperature.

21. 2. HOT AIR OVEN
• Kills by oxidation effects
• Utilizes dry heat to sterilize
• Temp- 50oC to 300oC.
• A holding period - 160oC for 1 hr
• Used to sterilise culture media,
petri dish, specimen
bottle,culture bottle and test
tubes,liquid paraffin

22. ❖ Time-temperature combinations
TEMPERATURE HOLDING TIME
160 oC 120 minutes
170 oC 60 minutes
180 oC 30 minutes

23. STERILISATION CONTROL
❖ Spores of nontoxigenic strain of Clostridium
tetani

24. MOIST / STEAM HEAT STERILISATION

25. TEMPERATURE BELOW 100o C
(PASTEURISATION)
.
❖ HOLDER METHOD – Heating
at 63o C for 30 minutes.
❖ FLASH PROCESS – Heating at
72o C for 15-20 seconds.

26. Vegetative bacteria are killed at 90-100 o C
❖
❖
❖
Requires immersion in water and boiling for
10-30 minutes
Promoted by addition of 2% sodium
bicarbonate
TEMPERATURE AT 100o C (BOILING)

27. STEAM AT ATMOSPHERIC PRESSURE
(TYNDALLISATION)
❖ Uses free steam at normal atmospheric
pressure i.e. 760 mmHg for 60 minutes.
PRINCIPLE - The first exposure kills all vegetative
bacteria and spores which survived the
heating process will germinate and are killed
in subsequent exposure.

28. TEMPERATURE ABOVE 100O C (AUTOCLAVES)
❖ Most reliable method of sterilisation.

29. Works on the
principle of
Steam under
pressure.
• Invented by Charles
Chamberland in 1879.

33. ❖
Various combinations of temperature, pressure and
holding times are used for sterilisation with
SATURATED steam.
PURE, DRY,
i.e. free from admixture with
air or other non-condensable gas
i.e. free from suspended
droplets of condensed water
i.e. in free molecular balance
with water from which it is formed

34.  PHYSICAL
 BIOLOGICAL INDICATORS
 CHEMICAL INDICATORS

35. STERILISATION CONTROL
❖ Bacterial spores – Bacillus stearothermophilus
❖ Thermocouple
❖ Brown’s test
❖ Autoclave tape

37. FILTRATION

39. CANDLE FILTERS
Hollow ‘Candle’ form
❖
❖ Used for purification of water

40. ❖ 2 types-
• Unglazed Porcelain filters eg-
Chamberland and Doulton filter
• Diatomaceous earth filters eg- Berkfeld and
Mandler filter

41. ASBESTOS FILTERS
❖ Disposable, single use discs with
high adsorbing capacity.
❖ Discarded – Cariogenic potential
❖ Examples – Seitz and Sterimat filter.

42. MEMBRANE FILTERS
❖ Made up of variety of polymeric materials
such as cellulose nitrate, cellulose diacetate,
polycarbonate and polyester.
❖
•
•

43. AIR FILTERS
❖ Mainly HEPA (High Efficiency Particle
Arresters) filter is used.

44. RADIATION

45. IONISING RADIATION
• Lethal action – breakdown of single stranded
or sometimes double-stranded DNA and effect
on other vital cell components.
• Cold sterilisation.
• X-rays, gamma rays and beta rays

46. NON-IONISING RADIATION
❖ Electromagnetic rays with wavelengths
longer than those of visible light are used.
❖ Ultraviolet and infrared rays

47. CHEMICAL AGENTS
⚫ Alcohols – ethyl, isopropyl, trichlorobutanol
⚫ Aldehydes – formaldehyde, glutaraldehyde
⚫ Dyes
⚫ Halogens
⚫ Phenols
⚫ Surfaceactiveagents
⚫ Metallicsalts
⚫ Gases – ethyleneoxide, formaldehyde, betapropiolactone.

48. Level of Disinfectants
• 1. High-level disinfectants
• 2.Intermediate-level disinfectants
• 3.Low-level disinfectants

50. MODES OF ACTION OF CHEMICAL DISINFECTANTS
⚫Proteincoagulation
⚫Disruption of cell membrane
⚫Removal of freesulphydryl groups
⚫Substrate competition

51. ALCOHOLS
⚫ Ethanol (80% v/vethyl alcohol)
or 2-propanol (60-70% v/v iso-
propyl alcohol) solutionsare
used to disinfectskinand
decontaminateclean
surfaces.

52. ALDEHYDES
Formaldehyde
Glutaraldehyde
Ortho- phthaladehyde

53. formaldehy
de
⚫Formalin is 37% w/v formaldehydegas in water.
⚫Spectrum: Activeagainst most microorganisms.
⚫Bactericidal, sporicidal, virucidal.
⚫13% v/v formalin is agood decontaminant (but has an
irritating odour).
⚫8% v/v formalin in 80% v/valcohol is effectiveagainst
vegetative bacteria, spores and viruses.

54. GLUTARALDEHYDE:
⚫Concentration: Glutaraldehyde is commercially available
as 2% w/v aqueous solution which must be made alkaline
to "activate" (e.g. byaddition of 0.3% sodium bicarbonate).
⚫A 2% glutaraldehydesolution, forat least 10 hours, can be
used to sterilize heat labile items.

55. Use: for instruments such as
cystoscopes, bronchoscopes, corrugated rubber anesthetic
tubes, face masks, endotracheal tubes, metal
instruments, polythene tubing.

56. HYPOCHLORITE:
⚫These are inexpensive, broad spectrum chlorine releasing
disinfectants of choice against viruses, including hepatitis
B virus.
⚫Aqueoussolution of sodium hypochlorite (5.25%) is called
household bleach.
⚫It is used in aconcentration of 0.2-1% depending upon the
circumstances.

57. PHENOLS
• Effective against bacteria
(especially gram +ve bacteria)
and enveloped viruses.
• Used for decontamination of the hospital
environment, including laboratory surfaces.
• Ex
cresol,chlorhexidine,chlorxylenol,hexachlorophines

58. HALOGENS
Commonly used
disinfectants
Bactericidal,sporicidal,vi
rucidal
2% iodine in 50%
alcohol(tincture) which
kills more rapidly and
effectively than alcohol

59. IODINE COMPOUNDS
⚫Iodine is used in aqueous oralcoholic solution.
⚫Rapidlyeffectiveagainst most microorganisms.
⚫Concentration: Usuallydiluted to 1% w/v free
iodine, optimum pH neutral toacid.

60. QUATERNARY AMMONIUM COMPOUNDS
⚫Quaternaryammonium compounds are positivelycharged
(cationic) surface-activedisinfectants.
⚫Effectiveagainst Gram-positive bacteriaand lipid-
containing viruses.
⚫Not recommended as general disinfectants (they have a
narrow antibacterial spectrum).
⚫Inactivated by proteins, soapand anionicdetergents.
⚫Eg. Benzalkonium chloride, alkyldimethylbenzyl
ammoniumchloride, and cetylpyridiniumchloride.
⚫Used for cleaning of floors of hospitals.

61. Gases
⚫Ehylene oxide
⚫It isan alkylating agent.
⚫Exerts lethal effecton proteins of bacteria.
⚫It is gas at ordinary room temperatureand active againstall
typesof bacteriaand spores.
⚫It has got agood degree of penetration power, even through
plastics.

62. ETO MACHINE
.

63. BETAPROPIOLACTONE (BPL)
⚫It isa condensation product of ketoneand formaldehyde
having a boiling pointof 163’C.
⚫It iscapable of killing all microorganisms including viruses.
⚫Uses: Although BPL has a low penetrating poweras a
gas, but it is believed to be moreefficient forthe purposeof
fumigation.

64. Surface active agents
• 1.Acetyl trimethyl ammonium bromide
• 2.Benzalkonium chloride

65. Metallic Salts
• 1. silver
• 2.copper
• 3.Mercury salts

66. Dyes
• 1. Aniline dyes
• 2. Acridine dyes

67. ⦁ Sterilization and Disinfection are costly and
time consuming process
⦁ However it is essential in all health care
facilities to avoid spread of disease.
⦁ It depends on the ethics of the instrument
users
⦁ Users should keep in mind that contaminated
instrument present risk to patient as well as
the user himself.

68. Thank you